This invention relates to an electromechanical actuator which comprises a body element and an elongated interaction element, wherein one of the elements includes an electromagnetic means and the other element includes magnetic material. The term xe2x80x9cmagnetic materialxe2x80x9d as used in this specification includes ferromagnetic material and permanent magnet material. The elements are arranged with respect to each other so that a rotational motion may be imparted to the interaction element by a magnetic field created by the electromagnetic means.
Publication FI 1000907 shows an electromechanical cylinder lock arrangement which comprises a body part of the lock and, inside thereof, a lock cylinder, which in the open position of the lock mechanism is turnable relative to the body part, and a blocking means functionally dependent on an electronic code and which in its locking position impedes turning of the lock cylinder with regard to the body part independent of the lock mechanism. The blocking means comprises an electromechanically turnable blocking member, which is adapted to a guiding groove made in the lock cylinder or in a turnable member continuously turning therewith so that in its locking position it impedes the free turning movement of the lock cylinder relative to the body part. In this solution the blocking member is turnable and thus it requires always a guiding groove to be arranged in and this in turn results in more space consuming arrangement.
An arrangement for blocking rotation of a locking apparatus is shown in DE 4029208. The solution is, however, very complicated with numerous components and therefore also for example its reliability is questionable.
In the field of locking and precision mechanics there is demand for an electromechanical actuator which is fairly mall in size, simple in construction and reliable, and by means of which it is possible to provide or allow a desired movement of a member and thus accomplish or stop an activity. The demand of electric power should also be kept reasonable, so that a simple, safe and cost-effective power source arrangement may be used.
It is an object of the invention to provide such an actuator. It is also an object of the invention to provide an actuator which is more advanced and reliable and less space consuming than those of prior art.
According to the invention the interaction element is rotatable between two rotational positions by changing polarity of the electromagnetic means so that in a first rotational position the interaction element is displaceable along its rotation axis by an external force. The interaction element receives the external force by virtue of its being disposed in the body element so that one end is accessible at least to such an extent that it is capable of receiving the external force. The interaction element is arranged to co-operate with the body element in a manner such that they together define the range of movement of the interaction element relative to the body element. According to a preferred embodiment of the invention an end of the interaction element is arranged to co-operate with guiding surfaces inside the body element in a manner such that they together define the range of movement of the interaction element in the axial direction.
In the body element there is favorably a limit stop means for restricting the range of rotation of the interaction element and hence for defining the two rotational positions. In this manner the consumption of electric power may be minimized because an electric pulse is sufficient to activate the rotational movement of the interaction element and current need be supplied for only a short period in order to rotate the interaction element from one limit position to the other and maintain it at this position. The solution is also reliable. In practice the range of rotation of the interaction element is preferably about 60xc2x0-90xc2x0.
For controlling the axial movement of the interaction element the interaction element has an inner end which is rotationally asymmetrical. Preferably, the inner end is delimited by two parallel surfaces, in the manner of a bar, and the guiding surfaces of the body element are parallel and define a chamber which is slot form for receiving the inner end of the interaction element in one rotational position of the interaction element. Then the periphery of the chamber may comprise a step-wise counter surface. Additionally the chamber contains a release spring for the interaction element. Alternatively the chamber may be defined between bevelled guiding surfaces, which are arranged to guide the axial return movement of the interaction element.
For ensuring that the interaction element remains in the rotational position to which it is rotated by the electromagnetic means in the event of possible external magnetic fields or other disturbances, such as vibration, the body element may be provided with a permanent magnet, by means of which the interaction element may be maintained at the rotational position to which it is turned by the electromagnetic means without continuously energizing the electromagnetic means.